System for use in conducting aircraft check lists

ABSTRACT

The system is for use in an aircraft, and it includes a number of pre-recorded messages or check lists, either emergency (in which case selection is automatic) or normal operational. Each message includes a number of separate items arranged in sequence. A desired list is selected either manually by the pilot or automatically by an emergency sensor, and a pre-recorded audio signal announces the first item over a speaker. The tape is then shut off, giving the pilot time to check the item. The pilot, when he is satisfied the item is operational, presses a reply bar to proceed with subsequent items. The tap re-winds automatically when the end of a message is reached and shuts down at the start of message position. In the case of an emergency, the system will interrupt a previously selected message if it is also not an emergency check list, return to the start of the proper emergency check list, and transmit an emergency radio signal. Circuitry permits repetition of an item if desired; and the pilot may selectively reset the message in high speed before completing it.

United States Patent Dickinson 1541 SYSTEM FOR USE IN CONDUCTINGAIRCRAFT CHECK LISTS [76] Inventor: Clarance B. Dickinson, Tower 6,

Bath & Tennis Club, North Green Bay Rd., Lake Bluff, Ill.

[52] US. Cl...340/27 R, 179/100.2 S, 179/1002 MD [51] Int. Cl. ..G08g5/02 [58] Field of Search...340/27 R, 221; 179/1002 MD,

[56] References Cited UNITED STATES PATENTS 3,059,062 10/1962 Ojala..l79/l00.1 3,294,924 12/1966 Fein ....l79/100.2 MF 3,298,010 1/1967Dubosq et al.... ....l79/l00.2 MF 3,015,702 l/l962 Vogel et al...340/221 2,718,628 9/1955 Bartlett et a1 ..340/27 R @ITEH mm RESETKAUDIO'CHECIK' P PRE START per.

[ 1 Jan. 23, 1973 Primary ExaminerKathleen l-l. Claffy AssistantExaminer Thomas L. Kundert Attorney-Dawson, Tilton, Fallon & Lungmus[57] ABSTRACT The system is for use in an aircraft, and it includes anumber of pre-recorded messages or check lists, either emergency (inwhich case selection is automatic) or normal operational. Each messageincludes a number of separate items arranged in sequence. A desired listis selected either manually by the pilot or automatically by anemergency sensor, and a pre-recorded audio signal announces the firstitem over a speaker. The tape is then shut off, giving the pilot time tocheck the item. The pilot, when he is satisfied the item is operational,presses a reply bar to proceed with subsequent items. The tap re-windsautomatically when the end of a message is reached and shuts down at thestart of message position. In the case of an emergency, the system willinterrupt a previously selected message if it is also not an emergencycheck list, return to the start of the proper emergency check list, andtransmit an emergency radio signal. Circuitry permits repetition of anitem if desired; and the pilot may selectively reset the message in highspeed before completing it.

5 Claims, 6 Drawing Figures ire-"gaz 3 PAIENTEDmza 1915 SHEET 3 BF 3 6E5 hi SPEU LLQUNIU SYSTEM FOR USE IN CONDUCTING AIRCRAFT CHECK LISTSRELATED APPLICATION This is a continuation-in-part application of mycopending application, Ser. No. 841,675, filed June 26, 1969 and nowabandoned.

BACKGROUND OF THE INVENTION 1. Field of the Invention The presentinvention relates to a system which is installed in an airplane and isused in assisting a pilot to check various items that are required, forexample prior to take-off, prior to landing, etc.

Normally, there are a number of check lists that a pilot must routinelygo through in order to operate the airplane. For example, there may be aPre-Start check list which must be gone through even before starting theengines, a Pre-Flight check list or Pre-Take Off check list, a Landingcheck list, and so on. Normally, the check lists are prepared insequential order on a paper, and a co-pilot reads the item to the pilotwho then makes the cheek and reports back to the co-pilot. During thistime, the entire attention of the co-pilot as well as the pilot must begiven to conducting the check lists.

2. Prior Systems It has been suggested to pre-record certain checklists, for example on magnetic tape, so that the pilot may play the tapeand conduct the check list. Such systems do not permit flexibility inpermitting the pilot to proceed at his own speed. That is, the actionsrequired of a pilot in a Landing check list may be performed morerapidly than the actions required in a Pre- Start check list when theengines are not even started. Further, such systems make no provisionfor incorporation of emergency check lists.

SUMMARY The present invention provides for a number of check lists(sometimes referred to as messages) both normal operational check listssuch as Pre-Start, Pre- Take off, Landing, etc. and emergency checklists. If desired, there may be a priority in the emergency check lists.

The pilot is permitted to select one of the desired pre-recorded checklists by means of the dial, and visual indicia indicate to the pilotwhich check list he is running through. On each of the check lists,individual items are recorded so as to be played back over a headset orspeaker to be heard by the pilot, and after each item is played back,the tape is stopped, but the system remains operational. After the pilothas performed the required function, he presses a reply bar which causesthe next recorded item to be plated back. Thus, the pilot may proceed athis own speed; yet, the co-pilot or other assistant is completely freedfrom the menial task of reading and checking a list. That is, theinvention allows one crew member to handle all the check listprocedures, and frees the remaining crew to stay fully oriented towardthe approach of any aircraft in the flight area. As most lists areperformed in high density areas, it is felt that this advantage willgreatly enhance aircraft safety.

At night, the inventive system permits the selection and performance oflists in areas of critical density without lights for illumination thatmight disturb a pilots night vision. Further, in emergency situations,the system completely frees remaining crew to handle the aircraft orassist in carrying out procedures other than calling off items to bechecked. The system enables the crew to carry out Pre-FIiglit checkprocedures faster, thereby expediting departure of aircraft.

The system contains provisions for deferring any standard check listitem with the visual indication that one item has been deferred and mustbe completed before the check list is complete. Further, an emergencyautomatically triggers an announcement to the pilot over a speakersystem as to what the emergency is and applicable check proceduresimmediately follow for assisting the pilot in isolating the fault. Theautomatic emergency detection system further energizes a broadcast overthe standard emergency channel which is 121.5 KI-Iz.

Other features and advantages of the present invention will be apparentto persons skilled in the art from the following detailed description ofa preferred embodiment wherein identical reference numerals will referto like parts in the various views.

THE DRAWING FIG. I is a front elevational view of a pilot's controlpanel of the type employed by the present invention;

FIG. 2 is a schematic representation, partially broken away, of themagnetic tape on which messages are recorded;

FIG. 3 is a functional block diagram of the selection gates for therecorded messages and the audio portion of the system;

FIG. 4 is a schematic diagram, partially in functional block form,illustrating circuitry for controlling the tape transport;

FIG. 5 is a functional block diagram of the electronic circuitry for apreferred embodiment of the invention; and

FIG. 6 is a circuit diagram, partially in functional block form, of thedeferred item function.

DETAILED DESCRIPTION Referring first to FIG. 1, reference numeral 10generally designates the faceplate panel of a plug-in module adapted tobe fitted into the instrument panel of an aircraft and easily accessibleto a pilot or operator. The controls utilized by the pilot include anon/off switch 11 which also includes a deferred item position, astart-reply bar 12 which controls a switch which is spring-biased in aforward (open) position, an item repeat push button switch 13 which isalso spring-biased in a forward (open) position, a manual reset pushbutton switch 14, also spring-biased in a forward (open) position, avolume control knob 15 for adjusting the volume of the audio signal thatis: pre-recorded on the tape, a selector switch 16 which is peripherallyar ranged relative to the volume control knob 15 and which selects oneof the pre-reco'rded messages, and a display window generally designated17 for indicating by means of alpha-numeric indicia which of theprerecorded messages has been selected by the knob 16. Each of thetitles of the pre-recorded messages, such as the Pre-Start" check list(as illustrated), Pre-Take Off" etc., are printed on a band of plasticand gears move the spools on which the film is mounted in response tothe pilot's turning the knob 16 so that the correct title for theselected checklist is displayed. However, any number of well knownmechanisms may be used for performing this function.

Turning now to FIG. 2, a magnetic tape designated by T, is shown in theform of an elongated strip. At the center and ends of the tape there areportions designated 18 and 18a respectively from which the oxide coatingof the tape is removed to provide a window (i.e. translucent ortransparent portion). The ends of the tape are wound on the two reels ofa magnetic tape transport which may be of the type sold as model DP bythe Kinelogic Corporation, Pasadena, California and corresponding tomilitary designation RO-254A/A SQ. In this type of tape deck, the tapeis provided in an enclosed cartridge, and there are separate heads forerasing, for recording, and for playback. There is also provided asource of light on one side of the tape and two photocell sensors on theother for detecting respectively the center of tape position (window 18)or the end of tape position (window 18a). The center of tape position issometimes referred to herein as the Start of Tape or S.O.T., signal, forshort. As will be made more clear in subsequent discussion, when theS.O.T. signal is sensed, the drive motor for the tape deck is shut off,and the tape may be moved in either direction.

The tape T in the illustrated embodiment is arranged in eight separatetracks, and these are designated respectively Tl-T8. Tracks Tl-T4 startat the center of the tape (that is, adjacent the start of tape window18) and extend to the left end of the tape. Tracks T5-T8 start thecenter of tape and extend to the right end of the tape. Each of thetracks Tl-T8 has a separate recorded message, usually comprising anumber of consecutively located individual instructions (sometimesreferred to as items). For example, the track T8 is showndiagrammatically as including two separate items designated Item 1" andItem 2, to be followed by a number of additional items. Each of theitems is separated by a tone, referred to the end of item tone, whereasthe very end of the track includes an end of item tone followed by anend of tape tone. The tones involved may be 3.5 KHZ signals, the end ofitem tones occurring for less than 2-5 seconds and the end of tape toneoccurring for 0.5 seconds in addition to the last end of item tone.

Persons skilled in the art will appreciate that the invention is notlimited to any particular number of tracks, nor to any particularcombination of emergency or non-emergency checklist, nor to anyparticular tape deck. For convenience, therefore, the subsequentdescription will relate to eight separate tracks, three of which havepre-recorded emergency messages and the remaining of which arenon-emergency messages such as check-lists. It will also be appreciatedthat any number of playback heads may be used, and for convenience itwill be assumed that there are four, one for each of the double sets oftracks (each set comprising one track to the left of the center positionand one to the right ofit).

The selector switch 16 is a rotary switch having nine differentterminals including a center one which is connected to a source of powerand is provided with a moveable contact for engaging any one of theremaining light terminals. The switch is settable to the eight differentpositions for the purpose of connecting the source of power to one offive different output lines, two of which are shown in FIG. 3 anddesignated respectively S1 and S5, the other lines being similar instructure and performing a function similar to the one to be describedin connection with lines S1 and 5-5. Line 5-] is coupled to one input ofan AND gate 25 and line 8-5 is connected to a similar input of an ANDgate 26, the other inputs of the AND gates 25 and 26 is a signaldesignated W. The signal W is the inversion of the emergency signal thatis, when an emergency arises a signal is generated, and the negative ofthat signal (as by feeding it through a signal inverter) is coupled tothe other inputs of the AND gates 25 and 26. The AND gates 25 and 26 aredigital logic gates ofa conventional type which generate an outputsignal only when both of the input signals have a logic 1 present. Forpurposes of explanation it will be assumed that a logic 1 is somepositive voltage and a logic 0 is ground, but the invention is not solimited. Thus, in an emergency situation the AND gates associated withthe outputs from the channel selector switch 16 are disabled. The outputof the AND gate 25 is connected to the enable lead of a gate 27, and theoutput of the AND gate 26 is connected to a similar enable lead of agate 28. The gates 27 and 28 are of a conventional type having a signalinput lead and an enable lead. The signal input lead is adapted toreceive a continuous signal such as an audio frequency signal, but thatinput signal will not be transmitted to the output of the gate unlessthere is also a digital 1 present at the enable lead of the gate. Theinput signals to the gates 27 and 28 are the output signals from theplayback heads of tracks T1 and T5 respectively. It will be appreciatedthat each of the playback heads associated with the non-emergency trackswill have a gate similar to the AND gate 25 and the gate 27 so that therecorded signal will be passed through its associated gate 27 only whenthe channel selector switch has selected that particular track and thereis not an emergency condition existing. The output of the gates 27 and28 as well as any similar gates are connected to a node designated 30.

The three emergency tracks T6-T8 are coupled to gates similar to gate27, two of which are shown and designated 31 and 32. The gate 31receives at its input the output of track T6, and the gate 32 receivesthe output of the playback head associated with track T8. The respectiveenable leads of the gates 31 and 32 (as well as any other emergencymessage gates) are coupled from specific emergency sensors. For example,if the pre-recorded message on track 6 is a checklist to be used duringthe case of an engine fire, a temperature or smoke sensor will bemounted within the engine so as to generate a signal when an engine fireoccurs. This signal will enable the gate 31 to couple the recordedmessage from track T6 to the node 30 while, at the same time, disablingthe gates (27, 28) and associated with the non-emergency messages.

The node 30 therefore carries the audio signal from either: (1) amanually selected pre-recorded checklist, or (2) an automatically sensedpre-recorded emergency message or checklist. The node 30 is connected tothe input of a pre-amplifier circuit 34, the output of which isconnected to an amplifier circuit 35. The volume control knob controlsthe value of a variable resistor generally designated by referencenumeral 36 which is connected between the input and output terminals ofthe amplifier 35. Thus, the control knob 15 determines the output volumeof the audio signal which is fed through a gate 37 and into the audiosystem, schematically shown by the speaker 39. The gate 37 is similar tothe previously described gates 27 and it includes an enable lead E whichreceives a signal designated Mute which, as will be described later is asignal generated, for example, during rewind of the tape so that theaudio noise does not appear on the speaker system. The output of thepre-amplifier 34 is also connected to the input of a high pass filtercircuit 40 (i.e. higher than audio frequency to block the signals of thepre-recorded messages) designed to sense the tone signal for the end ofitem tone and the end of tape tone. This signal is passed through anamplifier 41 and into two different detector circuits generallydesignated by reference numerals 42 and 43. The detector circuit 42includes a resistance-capacitance network including a resistor 44 and acapacitor 45 connected in circuit so that the signal on the capacitor 45builds up according to a predetermined time constant. When the signalreaches a certain level, a level detector circuit 47 generates an outputsignal, denoted the end of item signal. The detecting circuit 43includes a similar resistor and capacitor 49, 50 and diode 51. Thesignal building up on capacitor 50 when a tone is detected will generatean end of tape signal when it exceeds a threshold set by a leveldetector circuit 52. The time constant of the detecting circuit 42 isdesigned to be shorter than the time constant of the level detector 43that is, the end of tape signal is generated not by an end of item tone(which is not of long enough duration), but only when an end of tapesignal is present, lasting about 0.5 seconds longer than an end of itemtone.

it will be appreciated in the previous description that in reality thesignals picked up from tracks T1 and T5 are picked up from the samehead. Similarly, the track pairs T2, T6 and T3, T7, and T4, T8 arepicked up from individual heads.

Turning now to FIG. 4, the control (speed and reversing) of the tapetransport motor will now be explained in greater detail. The channelselector switch is again generally designated by reference numeral 16,and it is shown as having eight separate terminals or contacts and awiper arm. The wiper arm is connected to a source of power so as toenergize whichever of the contacts 51-88 are selected. The contactsSl-S4 (corresponding to tracks Tl-T4) are connected to separate inputsof an OR gate 60. Similarly, the contacts S5-S8 (corresponding to tracksTS-T8) are connected to inputs of an OR gate 61. The output of the ORgate 60 is connected to the set input of a flip flop 62; and the outputof the OR gates 61 is connected to the reset input of the flip flop 62.The flip flop 62 is of the type that its 1 output carries a signalwhenever a ground signal (or logic 0) appears at its set input, and thesame output carries a 0 when the reset input is similarly set. Whateverthe output state of the flip flop 62, it will be reversed when itstrigger input is pulsed. The trigger input of the flip flop 62 isreceived from an OR gate 64, the function of which will be described ingreater detail subsequently. The 1 output of the flip flop 62 isconnected to the coil of a relay generally designated by referencenumeral 65 which is the forward/reverse relay, controlling the reversingof the tape transport motor which is schematically shown within thedashed line 66. The motor has a set of high speed windings generallydesignated 67 and a set of low speed windings generally designated 68.The tape reels are schematically shown and generally designated 69 withthe playback heads schematically shown at 70. The coil of relay 65controls the switching of four separate switches, 65a-65d which are ineffect two double-pole, double-throw switches for reversing the currentto the windings 67 or 68, whichever is energized. As is conventional,the motor windings are capacitor-coupled to the power lines that feedthem. One of the power lines is designated 73 and the other isdesignated 74. The line 74 is connected to the wiper arm of atwo-position contact generally designated by reference numeral 75 whichis controlled by a relay, the coil of which is designated 77. Thecircuitry which energizes the coil of relay 77 will be described ingreater detail below.

The lines 73 and 74 are coupled to a power supply 80 (which may be theaircraft power supply) by means ofa set of normally open contacts 81which are actuated by the coil of a relay 82. The coil of relay 82 isconnected in series with a set of contacts 83 and a transistor 84, thecoil being connected to the collector of the transistor 84. Thetransistor 84, as shown, is normally biased in an on or conductingcondition, and the base of the relay is coupled by means of an invertercircuit 86 to the output of an OR circuit 87. Two inputs of the ORcircuit are from the center of tape photocell (schematically shown at 88and generating a signal when light is sensed through window 18 of thetape) and the other input being received from the previously describedlevel detector circuit 52 for end of tape signals.

The normally open contacts 83 are controlled by the coil of relay 90which is connected in series with the normally open contacts 91 of arelay 92. Also connected in series with the contacts 91 in coil 90 is aJ-K flip flop 93. A master memory circuit 94 is connected in circuit toenergize the coil of relay 92. The master memory circuit 94 may be aconventional memory circuit which is capable of being set and reset;whereas, the J-K flip flop is a type commonly known in the trade havinga set input, a reset input and a clock input. The signals present at theset or reset inputs are transmitted to the output terminals of the flipflop when a signal is received at the clock input of the flip flop.

Turning now to FIG. 5, the master memory 94 and the flip flop circuit 93are shown at the upper right hand corner as feeding a block functionallylabeled Control Circuitry of FIG. 4 including the circuitry previouslydisclosed in connection with FIG. 4 which need not be repeated here.

The Set input of the master memory 94 has two separate set inputterminals; one is connected to the output of a NAND gate 98. The memory94 is set on a 0 signal. A NAND gate is one in which the output signalis a 0 only when all the inputs are ls, otherwise the output signal isa 1. It is thus an inverting AND gate, and is commonly known. One inputof NAND gate 98 is received from the output of another NAND gate 99; andthe other input is received from a lead designated 100 and energized bya signal labeled SOT denoting the inverse of the Start of Tape signal.That is, a 1 signal will be present on the lead 100 to energize oneinput at the NAND gate 98 only when the tape is not in its centerposition (that is, when the tape is playing). The S OT signal isgenerated by a photocell, the output of which is passed through aninverter.

The function of NAND gate 99 is to rewind the tape to the start positionin high speed either upon pressing the reset switch 14 or upon theoccurence of an emergency and the tape is in the middle of a message.One input of the NAND gate 99 is coupled to the output of an Inverter112; the input of which is fed by a 1 signal I unless the Reset switch14 is depressed. The other input of the NAND gate 99 is received fromthe set output of a flip flop circuit 101. The flip flop circuit 101 isa conventional flip flop circuit having a set input (S), a reset input(R) and a trigger input (T). The set input is energized by the W signaland the trigger input is ener-' gized by the output of a NAND gate 102.The output of the NAND gate 102 is also connected to one input of an ANDgate 103, to one input ofa NAND gate 104, to an Emergency BroadcastTransmitter 102A, and to an inverter which generates a signal to disablethe gates which transmit the check lists non-emergency (see 27, 28 inFIG.-3). The reset input R of the flip flop 101 is received from the endof tape (EOT) signal (generated by the level detector circuit 52 of FIG.3). The EOT signal also is fed through an inverter circuit 106 to theother input of the AND gate 103. The output signal of the AND gate 103feeds the set (S) input of a memory flip flop circuit 107 which locksout other emergency check lists once one is being played. The resetinput of the flip flop circuit 107 is energized by an automatic resetcircuit designated 108 so that once the flip flop 107 is set, it may bereset only by turning off the power and turning it on again. The resetcircuit 108 generates an output signal only when power is turned on, andit may be of a conventional RC circuit of the type used to set flipflops and registers to an initial state when power is turned on.

The NAND gate 102 has three separate inputs, each energized by aseparate one of the automatic emergency sensor, schematically designatedby the block 109. The signal on each input line is normally a I, so thatthe output of NAND gate 102 is a I only when there is an emergencycondition. The output of the memory cireuit 107 is fed into an inhibitcircuit in the automatic emergency sensors 109 to inhibit thetransmission of a subsequent signal to the playback head selectioncircuitry when the memory circuit 107 is in a set condition. Thus, if anemergency arises, one of the outputs of the automatic emergency sensors109 will energize the NAND gate 102 which will, in turn, set flip flop107 through AND gate 103. At the same time, the state of flip flop 101is reversed so that if a non-emergency check list is being performed,the system is triggered into a reset condition, whereas if no list isbeing played, the selected emergency list will be started immediately.

The other input of the NAND gate 104 is received through an invertercircuit 110 from the lead 100, representing the SOT signal. The NANDgate 104 feeds one input of a NAND gate 111. The other input of the NANDgate 111 is received from the start-reply switch 112 on which there ispresent a 1 signal until the startreply bar 112 is depressed by thepilot. The output of the NAND gate 111 is a I only when all the inputsare ()s; and it is coupled through an inverter 111a to one input of aNAND gate 113, the other input of which is received from the output ofthe inverter 110. Both inputs to the NAND gate 113 will be 0's (to resetflip flops 93 and 94) therefore, when the tape returns to the centerposition, the operator is not pressing the startreply bar 112 and thereis no automatic emergency signal being generated.

The output of inverter 111a is coupled directly to the input setterminal (S) of the flip flop 93. The reset input of flip flop 93 isconnected to the output of previously described reset circuit 108 whichis also connected to the reset input of flip flop 94.

Turning now to the central portion of FIG. 5, there are two J-K flipflops designated respectively 116 and 117, each having a J input, a Kinput, a clock input (C), a first output labeled Q, a second outputlabeled 6 and a reset R. As is known in the art, a signal will appear atthe Q output if a 1 signal is present at the set input and a transientsignal is is transmitted to the clock input. These two flip flops andtheir associated circuitry and connections are sometimes referred tocollectively as the Item Repeat Counter (or Register) that is, thefunction of the logic associated with these two flip flops is to reversethe operation of the tape in response to a signal from the pilot so thatan item just completed will be repeated without going back to the startof the tape.

The item repeat switch is shown in electrical schematic in the lowerportion of FIG. 5 and designated by reference numeral 13a. When theswitch 13a is actuated it transmits a 1 signal to an OR gate 118 as wellas to an inverter circuit 119. The other input of the OR gate 118 isreceived from an AND gate 120; and the output of the OR gate 118 isconnected to the clock input of the J-K flip flops 116 and 117. The Qoutput of the flip flop 116 is directly connected to the J input of theflip flop 117, and the Goutput of the flip flop 116 is directlyconnected to the K input of the flip flop 117.

The 0 output of the flip flop 116 is also connected to one input of thepreviously described AND gate 64 (also seen in FIG. 4), the output ofwhich is connected to the trigger lead of flip flop 62 for reversing thetape drive motor when the Item Repeat switch is actuated. The output ofaNOR gate 115 (fed by inverter 1110) is connected to the reset inputs ofthe flip flops 116, 117 in the Deferred Item Counter.

The 6 output of the flip flop 116 is directly connected to the K inputof the flip flop 117 and to one input of an AND gate 123 and to oneinput of an AND gate 124. The other input of the AND gate 124 isreceived in the 6 output of the flip flop 117; and its output is fed toan inverter circuit 125. The output of inverter 125 is connected to aninput of the AND gate 120, to an input of an OR gate 130, and to theinput of an inverter a which has its output connected to an input of anAND gate 135. The other input of the AND gate 120, as already mentioned,is the End of Item signal. The Q output of the flip flop 117 is directlycon nected to the K input of the flip flop 116, and the Q output of theflip flop 117 in addition to being connected to one input of the ANDgate 124 is connected to the J input of the flip flop I16 and to aninput of a NOR gate 122.

A high speed (sometimes called reset) memory 127 which is a conventionalflip flop circuit having a set (S) and a reset (R) input its reset inputreceives and is triggered by the change of the OT signal. When the tapeis re-wound to the center position so that the QT signal goes from a lto a 0, the negative leading edge will reset the memory 127. The setinput of the reset memory 127 is received from the output of the NANDgate 98. The output of the high speed memory is fed directly to thespeed control (relay coil 77 of FIG. 4) and the motor control portion ofthe system to cause the tape transport motor to operate in high speeddurmg reset.

The output of the memory 127 is fed to an input of an OR gate 130, theother input of which is received from the inverter circuit 125 and theoutput of which is fed to mute the speaker in the system, and this maysimply be done by reverse-biasing a transistor coupling the output ofthe read head to the amplifier 35 of FIG. 3, and is well within theskill of the art. The output of the OR gate 130, therefore, mutes thespeaker. This occurs during high speed rewind and during the time atwhich the tone recorded on the tape are being read back. The output ofthe reset memory 127 also feeds an input of a NOR gate 133, the outputof which is connected to the trigger input of the flip flop 93. Theoutput input of the NOR gate 133 is ac coupled through a capacitor 134afrom the output of an inverter 134, the two inputs of which are receivedrespectively from the AND gate 135 and a monostable circuit 136. Theinput of the monostable circuit is received from the AND gate 123.

As mentioned, one input of the AND gate 135 is connected to the outputof inverter circuit 135a; the other input of the AND gate 135 isconnected to the E01 signal.

OPERATION To operate the system, the pilot or operator turns the switch11 (FIG. 1) to the ON condition to connect power to the logic circuitryand to the tape drive. At this time the tape will normally be in itscenter position. The operator then adjusts volume by means of the knob15 and selects which of the pre-recorded check lists he desires tocomply with using knob 16. The selection circuitry has already beenexplained in connection with the description accompanying FIG. 3 and themanually selected inputs T1-T5. Thus, the selected playback head will bedirectly connected to the pre-amplifier 34 of FIG. 3 and to the speaker39 through the amplifier 35 and gate 37. Preferably the title of thecheck list is recorded on film and mechanical means are provided formoving the correct title into the window 17 on the control panel 10 sothat the pilot knows that the check list he has selected is the correctone.

When the power is turned on, the reset circuit 108 generates a signal toreset flip flop 107 and to reset master memory 94 as well as flip flop93. The reset circuit 108 may be a resistor and capacitor circuit withan output transistor for amplification of the type which areconventionally employed in digital systems to insure that all flipflops, registers, etc. are set in the proper state when power is turnedon. If the playback head is not at a center of tape position (i.e. startof message), memory 94 and flip flop 93 will be set through inverter110, NAND gate 104, NOR gate 111 and inverter 111A; and the tape willbegin to play until an End of Item tone is sensed. If the pilot desiresto reset the tape, he presses the reset switch 14, the operation ofwhich will be explained presently.

To start a check list, the pilot presses the start-reply bar 12 to closethe switch at this time. Both inputs to NAND gate 111 are normally ls soits output will be a 0; when the switch 12 closes, the output ofinverter 111a will energize the set input to the master memory 94 (whichsets on a ground input). This will energize coil 92 (FIG. 4) to closecontacts 91. The same signal from inverter Illa will set flip flop 93,the output of which will energize coil (FIG. 4) to close contacts 83thus energizing coil 82 since transistor 84 is normally conducting.This, in turn, will close contacts 81 to supply power to the tape drivemotor (either forward or reverse depending upon which of the tracks ofthe tape have been selected).

At the same time, depression of the start-reply bar transmits a 0 to theinput of NOR gate 115; and since the other input of NOR gate 115 is also0 (the Q output of flip flop 116 being a 0 at this time), the output ofNOR gate 115 will go to a I until the start-reply bar is released, andthe transition from a 0 to a I will reset both flip flops 116 and 117 ifthey have not already been reset. The start-reply bar is alsoilluminated from the rear by means of two lamps and a holding relay (notshown) to indicate that the selected check list has been started.

The tape will then be driven forward and the first item of theprerecorded message will be played over the speaker 39 of FIG. 3. At theend of each item the level detector 37 will generate an End of Itemsignal which will be transmitted through the AND gate (the other inputalso being a l), thl inverter 134 and ac coupled to transmit a momentary0 to one input of the NOR gate 133. Since the output of the reset (orhigh speed) memory 127 is also a 0,.the momentary 0 from inverter 134will cause the NOR gate 133 to trigger the flip flop 93 to reverse itsstate. It will be appreciated that flip flop 94 is not reversed, and canonly be reversed by a signal indicating that the tape is at a centerposition. In order to then play the next item, the pilot must depressthe start-reply bar 12 again. This will then generate a signal to setthe flip flop 93 again and thereby energize the coil 90 as alreadydescribed. When the end of a message is reached, the EOT signal fromdetector 52 will trigger flip flop 101 to send the system into anautomatic reset mode in high speed.

If the pilot or operator desires to reset the message back to itsstarting position, he depresses the pushbutton 14 which will transmit a0 to NAND gate 99 which, in turn, will cause its associated input toNAND gate 98 to become a I. If the tape is not at the center position,both inputs to NAND gate 98 will. be a 1 and its output a 0. The changefrom a l to a 0 sets master memory 94 and sets high speed memory 127 sothat the reversing will be in high speed. The output of the high speedmemory 127 will trigger flip flop 93 through NOR gate 133 to reverse itsoutput states and start the tape drive motor after the reversingcontacts 65a-65d have been actuated. The high speed memory 127 will alsoenergive the mute lead through OR gate 130 and it will lock out theeffects of B01 signals by transmitting a l to the NOR gate 133. Theother input to AND gate 98 will be fed by a signal indicating that thetape is not at the center of tape position so that flip flop 93 willenergize the tape drive motor to rewind the tape in high speed. When thetape reaches its center position the SOT signal will be and the inverter110 will generate an output signal which will be fed to the NAND gate113 to reset flip flops 93 and 94 and de-energize the drive motor.

In order to understand the operation of the item repeat function,reference is made to Table I set forth below wherein the logic states ofthe O outputs of flip flops 116 and 117 are indicated by 0s and ls. Theleft column represents the state of the 0 output of flip flop 116 andthe center column represents the state of the 0 output of flip flop 117.

TABLE I FF 116 FF 117 Operation 0 Normal 1 0 Reverse l l 0 1 Forward 0 0Normal It will be recalled that every time the pilot presses thestartreply bar, the flip flops in the Item Repeat Counter (namely, 116and 117) are reset through NOR gate 115. Starting with the item repeatcounter in its normal state, that is, when the Q outputs of each of theflip flops 116 and 117 are in the 0 state, the system operates normally.When the pilot pushes the item repeat button, he eloses the switch 13 tosend a 1 signal through the OR gate 118 to the clock inputs of the flipflops 116 and 117. The flip flops, however, trigger on the negative edgeof the clock signal so that nothing happens until the operator removeshis finger from the switch 13a. Then, because the 6 output of flip flop117 has a 1 signal, that signal will be transferred to the J input offlip flop 116 so that its output will also become a 1; and the ItemRepeat Counter is in the state represented by the second line of Table1, namely when the Q output of flip flop 116 has a 1 and the 0 output offlip flop 117 has a 0.

When the 1 on the 6 output of the flip flop 116 goes to 0, the output ofAND gate 124 goes to a 0 and the output of inverter 125 goes to a l thustransmitting a mute signal to amplifier 37 through OR gate 130 andsending a 1 signal to AND gate 120 and inverter 135a. The AND gate 124is a decoder which generates a 1 signal at the output of inverter 125whenever the Item Repeat Register is in any state but that correspondingwith line 1 ofTable I, that is, during an Item Repeat Cycle. Thus, the lsignal at AND gate 120 permits subsequent EOI signals to pass through ORgate 118 to trigger the clock inputs to flip flops 116 and 117; and the1 signal to Inverter circuit 135a will disable AND gate 135 to preventsubsequent EOI signals from triggering flip flop 93.

When the pilot releases the Item Repeat switch, the state of flip flop116 switch, so that the AND gate 64 will be enabled to reverse thedirection of travel of the tape drive motor. Next, the pilot pushes thestart-reply bar to set flip flop 93, and the tape will be driven in areverse direction. The first thing that happens is that the read headwill pass over an End of Item tone which will pass through AND gate 120and OR gate 118 to pulse the clock inputs of the flip flops 116 and 117and thus cause them to assume the inputs state of line 3 of Table I. Thetape will continue to be re-wound until the read head passes over thenext previous End of Item tone which will generate a signal that willtrigger the flip flops in the Item Repeat Counter to assume the state ofline 4 of Table I. When this state is sensed by AND gate 123, it willtrigger monostable circuit 136 which will, in turn, transmit a signal toreverse the state of flip flop 93 and shut off the drive motor and alsoto reverse the state of flip flop 62 to again reverse the direction ofthe drive motor i.e. to cause it to be set up for forward (or original)direction of motion. However, the tape will not be moved in the forwarddirection at this time because the flip flop 93 has been reset. At thistime, the playback head will be in a position which is two End of Itemsignals closer to the center of tape than it had been before the pilotclosed the Item Repeat switch.

Now, the pilot may re-play the previously played item by pressing thestart-replay switch 12 a second time and holding it down until he hearsthe first tone subside. Operation thereafter is normal because hispressing the start-reply switch resets the Item Repeat Counter.

If an automatic emergency should arise, a first signal is generated byan appropriate sensing mechanism to select the proper one of the tracksT6-T8 by enabling its associated gate 31, 32. That the proper track willthen be coupled through the amplifiers to the speaker 39. Normally, allof the outputs of the generator are 1 s, so an emergency signal willenergize the NAND gate 102 which feeds an emergency broadcast radiotransmitter 102A to transmit an emergency on the universal emergencyfrequency. The gate 102 also triggers the flip flop 101 to reverse itsstate. Thus, if the tape were in the middle of a message, the drivemotor will be shut off, but if the tape were in the center, it will beturned on with the proper playback head selected. If the tape had beenrunning, the system goes through a complete reset cycle and then comesback to the center of tape. When the tape reaches the center position,master memory 94 cannot be reset because NAND gate 113 blocks reset inthe emergency condition. The combination of SOT signal and emergencycondition will give a restart through NAND gate 104 and NOR gate 111.If, on the other hand, the system had been off, the output of gate 104will change immediately without the reset because there is an SOT signalout of inverter 110. If the tape is in the middle of a message then theflip flop 101 is generating a 1 output signal to set the master memory94 and the reset memory 127 so that it will be reversed in state andtransmit a signal through NAND gate 99 and reset the tape to the startof tape position through circuitry which has already been described.When the tape reaches the Start of Tape position, the inverter willenergize the NAND gate 104, and a signal will pass through the NOR gate111 to set both flip flops 93 and 94 and the emergency message will beplayed.

At the end of each check list as well as at the end of each emergencymessage there will be generated an end-ofrtape (EOT) signal which willbe transmitted to trigger the flip flop 62 and to energize a second leadof the AND gate 103. The output of the flip flop 101 is transmittedthrough the NAND gate 99 to reset the tape to its start position. TheAND gate 103 generates an output signal when the OR gate 102 isenergized indicating that an emergency message is being played and whenan end of tape signal present. The output of the AND gate 103 sets aflip flop 107 to generate a signal which shuts off the system after theemergency message has been played. Thus, in the case of one emergencysignal being generated others cannot interrupt it although it will beapparent that an automatic emergency message will interrupt apre-recorded check list in progress. The flip flop 107 will be reset bythe circuit 108 only after the pilot turns power off and then back Whenthe pilot desires to skip an item on the check list, he turns the switch11 to the deferred item position. Referring to FIG. 6, it will be seenthat this position shorts two contacts which connect a free-runningvmultivibrator circuit 170 to energize a lamp driver 171 which thenfeeds a square wave signal to the filament of a lamp (or lamps) 172located behind the translucent cover for the start-reply bar, designated173. This will remind the pilot that he has deferred one item, but itdoes not otherwise affect operation.

Having thus described in detail a preferred embodiment of the inventivesystem it will be apparent to per sons skilled in the art that elementsmay be substituted for those which have been disclosed to performsimilar functions and that other modifications to the disclosedembodiment may be made while continuing to practice the inventiveprinciples; it is, therefore, intended all such modifications andsubstitutions be covered as they are embraced within the spirit andscope of the claims.

I claim:

1. A system for use in performing check lists in an aircraft comprising:a magnetic tape recorder with a reversible drive motor having high andlow speeds and a magnetic tape having a plurality of prerecorded checklists including normal check lists and emergency check lists, each checklist having a plurality of recorded items and an end of item signalafter each item, a start of message signal, and an end of tape signal,each emergency check list associated with a predetermined emergencycondition in said aircraft; an

emergency sensor associated with each emergency check list forgenerating an emergency signal in response to the occurrence thereof; aselection gate circuit associated with each recorded normal check listand actuatable by an operator to select non-emergency check lists; firstcircuit means responsive to the absence of a signal from said emergencysensors for permitting said selection gates to transmit a recordednormal check list only when there is no emergency; audio circuit meansreceiving the output signals of said selection gates for playingrecorded normal check lists and for generating an end of item signalwhen detected and an end of tape signal when detected; second circuitmeans including a start-reply switch actuatable by the pilot andbistable circuit means for energizing said drive motor when in a firststate and for stoppin said drive motor when in a second state, actuation0 said start-reply switch setting said bistable circuit to said firststate in the absence of an emergency signal; third circuit meansresponsive to an end of item signal for setting said bistable circuit tosaid second state to stop said drive motor after each announced item;fourth circuit means for reversing said drive motor in high speed inresponse to an end of tape signal while locking out said end of itemsignals; and fifth circuit means responsive to an emergency signal for'rewinding the tape in high speed if it is not at a start of messageposition and for selecting and playing an associated emergency checklist.

2. The system of claim 1 further comprising item re peat circuit meansincluding a switch actuatable by the pilot to selectively reverse saidtape one item and to reverse said motor back to a forward drive positionin response to a second-detected end of item signal while locking outsaid item repeat signal from said bistable circuit.

3. The system of claim 2 further comprising a deferred item switchactuatable by a pilot and blinker light means visible to said pilot forindicating that an item on a check list has been deferred.

4. The system of claim 1 further comprising emergency transmitter meansfor broadcasting an emergency radio message in response to an emergencysignal from any of said emergency sensors.

5. The system of claim 1 wherein said fourth circuit means furthercomprises means responsive to said start of message signal for stoppingsaid recorder after returning said tape to said start position.

1. A system for use in performing check lists in an aircraft comprising:a magnetic tape recorder with a reversible drive motor having high andlow speeds and a magnetic tape having a plurality of pre-recorded checklists including normal check lists and emergency check lists, each checklist having a plurality of recorded items and an end of item signalafter each item, a start of message signal, and an end of tape signal,each emergency check list associated with a pre-determined emergencycondition in said aircraft; an emergency sensor associated with eachemergency check list for generating an emergency signal in response tothe occurrence thereof; a selection gate circuit associated with eachrecorded normal check list and actuatable by an operator to selectnon-emergency check lists; first circuit means responsive to the absenceof a signal from said emergency sensors for permitting said selectiongates to transmit a recorded normal check list only when there is noemergency; audio circuit means receiving the output signals of saidselection gates for playing recorded normal check lists and forgenerating an end of item signal when detected and an end of tape signalwhen detected; second circuit means including a start-reply switchactuatable by the pilot and bistable circuit means for energizing saiddrive motor when in a first state and for stopping said drive motor whenin a second state, actuation of said start-reply switch setting saidbistable circuit to said first state in the absence of an emergencysignal; third circuit means responsive to an end of item signal forsetting said bistable circuit to said second state to stop said drivemotor after each announced item; fourth circuit means for reversing saiddrive motor in high speed in response to an end of tape signal whilelocking out said end of item signals; and fifth circuit means responsiveto an emergency signal for rewinding the tape in high speed if it is notat a start of message position and for selecting and playing anassociated emergency check list.
 2. The system of claim 1 furthercomprising item repeat circuit means including a switch actuatable bythe pilot to selectively reverse said tape one item and to reverse saidmotor back to a forward drive position in response to a second-detectedend of item signal while locking out said item repeat signal from saidbistable circuit.
 3. The system of claim 2 further comprising a deferreditem switch actuatable by a pilot and blinker light means visible tosaid pilot for indicating that an item on a check list has beendeferred.
 4. The system of claim 1 further comprising emergencytransmitter means for broadcasting an emergency radio message inresponse to an emergency signal from any of said emergency sensors. 5.The system of claim 1 wherein said fourth circuit means furthercomprises means responsIve to said start of message signal for stoppingsaid recorder after returning said tape to said start position.